Here are the key quotes from the North Korean leader's announcement, made at a meeting of the central committee of the ruling Workers' Party, as reported by the official KCNA news agency.

'Brilliant victory'

Kim described building North Korea's nuclear force as a "miraculous victory".

"The struggle of the Korean people who worked hard with their belt tightened to acquire a powerful treasured sword for defending peace was successfully concluded," he said.

He described Pyongyang's nuclear weapons as "the firm guarantee by which our descendents can enjoy the most dignified and happiest life in the world".

"No nuclear test and intermediate-range and inter-continental ballistic rocket test-fire are necessary for the DPRK now, given that the work for mounting nuclear warheads on ballistic rockets was finished," Kim added, using the acronym for North Korea's official name.

Security guarantee

The North Korean leader said Pyongyang was willing to "make positive contributions to the building of (a) world free from nuclear weapons... provided that the DPRK's might was put on the level wanted by it and it became possible to reliably guarantee the security of the state and the safety of the people".

Nuclear threat

"The DPRK will never use nuclear weapons nor transfer nuclear weapons or nuclear technology under any circumstances unless there are nuclear threat and nuclear provocation against the DPRK," the committee resolved after Kim's speech, according to KCNA.

Pivot to economy

With the goal of building a nuclear force achieved, Kim said North Korea would now focus "all efforts" on economic development.

"Our goal is to activate the overall national economy and put it on an upward spiral track and thus establish independent and modern socialist economy," he said.